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corolla 20-22 mm long, tube 7-9 mm, lobes 3.5-5.5 

 mm, pappus 18-19 mm, tawny, of 30-40 setae, longer 

 setae clavellate; anthers, including appendages, 

 7.5-8.5 mm long, free tips usually incurved; style 

 long-exserted to 1 cm beyond the corolla, tip to 

 joint of style 3.5-5 mm; achenes 5.5-6.5 mm long, 2 

 mm wide, light brown sometimes with purplish flecks 

 (adapted from Moore and Frankton 1963) . 



C. Local field characters: The dilated, lacerate- 

 fringed tip of the outer involucral bracts are 

 characteristic of Cirsium lonqistylum , although some 

 plants do not show this character well. It is 

 perhaps best distinguished from C. hooker ianum ^ with 

 which it may hybridize, primarily by the involucral 

 bracts. In C. hooker ianum , the bracts are not 

 dilated and fringed, but are moderately to strongly 

 hairy, while those of C. lonqistylum are glabrous or 

 nearly so. Recent keys separating C. lonqistylum 

 from other Cirsium species in Montana are in Dorn 

 (1984), and Hitchcock and Cronquist (1973). 



D. Identifying characteristics of material which is in 

 interstate or international commerce or trade: No 



interstate or international commerce or trade known. 



E. Photographs and line drawings: Color slides (p. 92) 

 are duplicates of those taken at the sites indicated 

 by the three-digit occurrence codes. Additional 

 slides of C. lonqistylum are housed at the office of 

 the Montana Natural Heritage Program, Helena, 

 Montana. 



4. Significance. 



A. Natural: Cirsium lonqistylum is one of 13 plant 

 species endemic to Montana. 



B. Human: None known. 



5. Geographical distribution. 



A. Geographical range: Cirsium lonqistylum occurs only 

 in central Montana, primarily in the Little Belt 

 Mountains, with a single recorded occurrence in the 

 Big Belt Mountains to the west. The range of 

 populations is indicated in Figure 1, p. 6. 



B. Precise occurrences. 



1. Populations currently known to be extant: In 



1990, four new populations were mapped, and the 



